This phase IIIB long term extension amendment to RP-54274-301 will expand the safety profile of riluzole beyond the double-blind phase. The multicenter study will have an open label and single riluzole treatment design. All patients will receive riluzole, 50mg, administered orally twice daily (BID) for a total daily dose of 100 mg. Should the efficacy results of the double blind study be better with higher or lower doses, the dose administered in the open label will be adjusted accordingly. Only safety data will be collected.